1. Field of the Invention
This invention relates to ruminant feeds and more particularly to a practical and inexpensive method for preserving the natural characteristics of ensiled fodders, while protecting the silage from deterioration and increasing its nutritive value.
2. Description of the Prior Art
Silage is widely used as a feed for ruminant animals such as cattle and sheep. It is produced by fermenting green fodders. The term fodders, as used herein, may be defined as any coarse vegetable material suitable for feeding to cattle. Particularly useful fodders include whole corn plant, corn stover, alfalfa, and other grasses.
A suitable green fodder, such as whole corn plant, is normally chopped and placed in a silo, a covered pit, or a package, to allow its conversion to silage. Initially, the plant cells of the fodder continue to respire, using the oxygen of the air entrapped in the fodder mass to form acids and to produce carbon dioxide. In a relatively short period of time, most of the oxygen is consumed. Depletion of the oxygen helps prevent the development of molds and other fungi.
Acid-forming bacteria multiply rapidly in the silage and attack the sugars contained in the fodder, producing carboxylic acids and some alcohol. The production of acid is important to the ensiling process because it prevents the growth of undesirable bacteria which cause putrefaction of the fodder. Palatability to the ruminant animal is best in feeds containing high proportions of lactic acid and low proportions of low molecular weight acids, such as acetic acid. The presence of these carboxylic acids is important to the palatability of the silage to ruminant animals.
Fermentation practically ceases when sufficient acid is formed, and if no air or other oxidizing agent is allowed to enter the ensiled mass of fodder, it will retain its nutritive value and palatability for long periods of time, such as a year or more. When air does penetrate to the ensiled fodder, mold and other fungi normally grow and destroy the contained acids, as well as the palatability of the silage. Putrefaction bacteria can then develop and cause further spoilage.
Air penetration into silage has long been a problem with the use of conventional silos, particularly at the surfaces of the silage and at cracks or openings in the silos. With the increased use of pits and other ensiling containers having low structural integrity, the intrusion of air and the degradation of ensiled fodders has become a more serious economical and animal health problem.
Most silages, including whole corn plant silage, contain some valuable natural protein, but usually contain less protein than is required for optimum ruminant growth. There has been a continuing scientific effort to overcome this deficiency, and to find a safe, economical, and effective silage preservative.
Freese, in U.S. Pat. No. 3,457,081, used ammoniated superphosphoric acid to produce a storage staple, palatable corn silage containing increased amounts of lactic acid. His process allowed the addition of urea and calcium carbonate, but did not teach the preservation of natural protein, prevention of molds, or the reduction of live microbial colonies in the silage.
Earlier Peebles et al in U.S. Pat. No. 2,579,609 had shown that dilute ammonia sprayed on leafy material immediately after field cutting was effective in preventing the deterioration of the carotene content in the ensiled material. No indication was presented of the natural protein preservation, nitrogen losses in the process, or the elimination of mold growth.
H. C. Millar, in U.S. Pat. No. 2,293,845, previously showed that fodders could be treated with ammonia at elevated temperature and pressure to increase crude protein content. Millar's treatment would appear to sterilize the fodders so that ensiling during or after the treatment could not be readily achieved. Huber and Santana in an article entitled "Ammonia Treated Corn Silage", published in the Journal of Dairy Science 55:489, showed that anhydrous ammonia could be used effectively in relatively small amounts to preserve corn silage and increase the crude protein content of the silage. However, they did not show that natural protein was effectively preserved, and that mold could be prevented. Handling anhydrous ammonia can be hazardous under conditions encountered during ensiling operations. Ammonia cannot be effectively used on fodders prior to their placement in an ensiling vessel because it is quickly lost by evaporation.
Simonet and Castle, in U.S. Pat. No. 3,063,839 claim the enhancement of naturally occurring crude protein, comprising amino acids and their complex products, such as peptides, by spraying freshly cut plant material with aqueous urea solutions just before drying at elevated temperatures. Carotene and Vitamin A were preserved. No teaching was made relative to silage, and ensiling of the dry plant material from their process was not suggested.
Snyder discloses a liquid ruminant feed supplement, in U.S. Pat. No. 3,934,041, which was prepared by the reaction of urea, formaldehyde and/or other aldehydes, molasses, and water. Snyder teaches the reaction of methylol ureas with sucrose under the influence of acid catalysts in the preparation of a liquid feed supplement. He does not propose the use of such a fluid in the preparation of silage and there is no indication that such would be effective.
O'Donnell, in U.S. Pat. No. 3,976,465 discloses a process for treatment of raw sewage or sewage sludge, containing pathogenic microorganisms, which are completely sterilized by treatment with a water soluble, monomeric, condensable methylol compound, and by condensing the monomeric methylol compound under acid conditions to form a waste product comprising a solid condensate having methylene bridges. O'Donnell found that it was necessary to pre-react the urea and formaldehyde to the methylol compound just prior to its use, rather than use an aged solution. All live microbes were eliminated in the process, so that fermentation and silage formation would not be possible using a similar procedure.
O'Donnell discloses, in U.S. Pat. No. 3,942,960 an apparatus for producing a granular, high nitrogen, odorless fertilizer animal feed by reaction of methylol urea with sterilized, partially dried, shredded sludge cake. He discloses further information on his waste treating and sterilizing process in U.S. Pat. No. 4,057,392 where he demonstrates sterilization and deodorization of sludge by treating it with N-methylol urea solution at a pH higher than 7, and then reacting the mixture at an acid pH of 3 to 5. No methylenediurea was present in O'Donnell's N-methylol urea solution. In U.S. Pat. No. 4,081,366 O'Donnell further elucidates his treatment of sewage sludge to produce a sterile solid hydrophobic waste with superior dewatering properties. He uses substantial amounts of freshly formed monomeric methylol urea solutions at pH 7 to 9 for complete sterilization of the wastes. The wastes treated include raw sewage sludge, raw sewage, solid carbohydrate and proteinaceous material recovered from industrial waste liquors from treatment of leather, wool, food, fish, meat, dairy products, and pharmaceutical wastes. Moore in U.S. Pat. No. 4,304,588 teaches a process for storage stable methylolurea-methylenediurea solution but discloses no information concerning possible use of this type solution as a silage preservative.
Thus, no teachings are available, or can be reasonably inferred, from the prior art, which would provide an economical method for the natural fermentation of fodders to palatable and efficaceous silages, while inhibiting the growth of mold, and substantially improving the nutritive value of the fodders. There is a need for the improvement of the nutritive values and palatability of silage and for inhibiting mold growth in silages while still allowing the silages to ferment naturally. This need has been made more urgent by the increasing use of the economical covered pits and large fodder bales instead of conventional cylindrical silos for carrying out the ensiling process of fodders for ruminant feeds. The term preservative used herein denotes a material which is added to fodder or silage in relatively small amounts to preserve the desirable nutritive and palatability properties of silage.